With the development of the cryogenic technology and the superconducting technology, a high magnetic field conduction-cooled superconducting magnet is convenient for system operation and has the advantage of compact size and light weight, due to its cryogenic system of a simple structure without the limitations of liquid helium or other cryogenic conditions. The critical technology of a conduction-cooled superconducting magnet system is that a cryocooler is employed to directly cool a superconducting magnet, which overcomes the conventional cooling method in which the superconducting magnet has to be cooled by using cryogenic liquid. With the development of the high temperature superconducting wire technology, Bi-based tape has a current density of Jc=104-105 A/cm2 within a temperature range of 20˜30K, even under a relatively high magnetic field. In such situation, the high temperature superconducting magnet that is cooled directly by a cryocooler has a relatively important meaning. The high temperature superconducting magnet operating at a temperature zone of 20K can make full use of the mature technology of a cryocooler of a temperature zone of 20K as well as the current carrying capacity of the high temperature superconductor and the high thermal conductivity and heat capacity of the superconducting tape, thus the high temperature superconducting magnet has a relatively high stability.
The high magnetic field superconducting magnet has important applications in the aspects of industry and scientific instrument. In situations such as multi-physical fields cooperatively act on a material under extreme conditions to study the physical characteristic, and neutron scattering, X-ray diffraction and synchronized radiation light sources are used to study the substance structure, a high magnetic field superconducting magnet with a certain size of crossing warm bore is needed to provide a background magnetic field for substance study. Such a superconducting magnet has an electromagnetic structure of relatively more complex as compared to that of an ordinary magnet, with a prominent feature of having a very large crossing warm bore so as to be suitable to access available magnetic field areas in lateral direction of the magnet. Thus, it has important applications in scientific instruments and other scientific study apparatus of extreme conditions, thereby providing innovative scientific study instrument and platform.
In this kind of superconducting magnet, due to a special crossing warm bore, the superconducting magnet will subject to a relatively strong electromagnetic force due to the interaction between superconducting coils under a high magnetic field. If the temperature is 4K, a method using combination of NbTi and Nb3Sn can generate a magnetic field of 18 T, and when the operating temperature is 2.2K, it can provide a central magnetic field up to 21 T. Recently, with the successful development of Nb3Sn superconducting wire having high current density, the superconducting magnet can provide a maximum magnetic field up to 22.3 T when the operating temperature reaches 1.8K.
In order to access the magnetic field zone in multi-dimensional directions, the superconducting magnet having super-large gap separates the superconducting coils along the direction of the magnetic field, thereby forming a relatively strong magnetic field area which can be accessed simultaneously in both the vertical and parallel directions of the superconducting magnet. Currently used low temperature superconducting magnet has a separation gap less than 20 mm, the system thereof is merely capable of providing a maximum magnetic field of 15˜17 T. In order to obtain a superconducting magnet system with coils separated by a large crossing warm bore, which has simple process and low fabrication cost, and will become an innovative superconducting magnet that can be used in combination with special material processing, X-ray, neutron scattering, other high temperature condition, high-pressure condition and associated scientific instrument, a high magnetic field magnet structure having a crossing warm bore over 100 mm is required, so as to provide a magnetic field exceeding 10 T. This magnet enables samples or other instruments to reach the relatively strong magnetic field area from different directions, thereby forming a high magnetic field magnet system that operates stably and can be applied to scientific instruments as well as scientific apparatus used for study under extreme conditions.